Ok, so I will assume you were born in 1981. You are a yin guy. And 38-10 is 28. Your girl is also ying. This union works in a social aspect, but not in sex... I am sure she is better than the hand, but there can be an improvement. You mentioned she is wife material, so I assume she is good looking or nice, loyal, and a honest person. You should keep her, but start to look at other prospects. You could also marry her, but look at other women for a change.
I can tell you who is yang, and get well with you. So girls born in years (1988, this is your best shot) 1990, 1992. You may deal with girls born in 1982 and 1980, and also 1978.
The other women may posses social issues. Communication may be a problem.
I deal a lot with this. The women I like don't communicate with me smooth, and the ones I don't like, can hold a conversation with me easily. This is many times very challenging for me. The passion becomes a torment. Frustrations mounts on. However, I don't have the sex problem you have. I have had some experience with women I don't get along well in sex, but such relations are temporary.
Now, my advice is practical and the source comes from my own personal experience, observations and reading of oriental culture.
I cannot teach about attraction or pick up lines. You seem to be doing well in this area.
You should not go around asking women, their date of birth. However, I am good at telepathy. Yesterday, there were some female coworkers smoking and chatting at work. I hover over the group, because I am interested in one and they all said their age. Don't go out asking about this, just date the woman and if you dont like her, move on.
You should think about your previous girlfriends and make a contrast between that girl and this one.
Alternatively, all women in escort business are yang.. So if you want to know the difference quick enough, you know what to do.